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#include "src/tint/lang/hlsl/writer/raise/fxc_polyfill.h"

#include "src/tint/lang/core/ir/block.h"
#include "src/tint/lang/core/ir/builder.h"
#include "src/tint/lang/core/ir/exit.h"
#include "src/tint/lang/core/ir/loop.h"
#include "src/tint/lang/core/ir/switch.h"
#include "src/tint/lang/core/ir/validator.h"
#include "src/tint/lang/core/type/manager.h"
#include "src/tint/utils/containers/vector.h"
#include "src/tint/utils/ice/ice.h"
#include "src/tint/utils/result/result.h"

namespace tint::hlsl::writer::raise {
namespace {

using namespace tint::core::fluent_types;  // NOLINT

/// PIMPL state for the transform.
struct State {
    /// The IR module.
    core::ir::Module& ir;

    /// The IR builder.
    core::ir::Builder b{ir};

    /// The type manager.
    core::type::Manager& ty{ir.Types()};

    /// Process the module.
    void Process() {
        for (auto* inst : ir.Instructions()) {
            if (auto* swtch = inst->As<core::ir::Switch>()) {
                // BUG(crbug.com/tint/1188): work around default-only switches
                //
                // FXC fails to compile a switch with just a default case, ignoring the
                // default case body. We work around this here by emitting the zero case as a
                // fallthrough to the default case
                if (swtch->Cases().Length() == 1 && swtch->Cases()[0].selectors.Length() == 1 &&
                    swtch->Cases()[0].selectors[0].IsDefault()) {
                    swtch->Cases()[0].selectors.Push({b.Zero(swtch->Condition()->Type())});
                }
            }
        }
    }
};

}  // namespace

Result<SuccessType> FxcPolyfill(core::ir::Module& ir) {
    auto result = ValidateAndDumpIfNeeded(ir, "FxcPolyfill transform");
    if (result != Success) {
        return result.Failure();
    }

    State{ir}.Process();

    return Success;
}

}  // namespace tint::hlsl::writer::raise